The biceps is a large muscle situated on the front of the upper arm between the shoulder and the elbow. It is composed of two heads, the long head and the short head, which arise on the scapula and join to form a single muscle belly that is attached to the upper forearm. The biceps brachii muscle primarily functions to flex the forearm and supinate the forearm. It is also a powerful supinator of the forearm due to the distal attachment of the muscle at the radial tuberosity, on the opposite side of the bone from the supinator muscle. The biceps is one of three muscles in the anterior compartment of the upper arm, along with the brachialis muscle and the coracobrachialis muscle, with which the biceps shares a nerve supply. The musculocutaneous nerve (C5-C6) innervates the biceps brachii muscle, and the muscular branches of the brachial artery supply blood to the muscle.